The Vertical Structure of Spiral Disks

该项目包括一项观测活动，以确定大型螺旋星系盘中的质量分布，从而限制暗物质在这些系统内部区域的重要性。首席研究员，与以前的NSF的支持，领导了特殊用途的积分场摄谱仪（或积分场单元，IFU）的发展，用于映射星系中恒星和气体的运动。有了这个仪器，他最近完成了大质量巡天，获得了面向视线的星系盘的多色宽带成像和积分场旋转和速度色散图。这些数据表明，星系盘的质光比预期的要低，这意味着没有大量的微弱的、质量非常低的恒星，并且暗物质晕即使在星系的内部区域也是动态重要的。然而，这些结论被沿视线沿着的盘的实际厚度的不确定性所削弱。为了纠正这种情况，首席研究员，他的合作者和研究生将进行进一步的观察，重点是类似的星系，这些星系的方向与视线平行。具体来说，他们将（1）在战略性地选择的宽和窄红外光谱波段对20个星系进行光度测量，这将允许分离不同年龄的恒星群体;（2）对盘边缘的旋转速度和速度分散进行IFU测量，作为到银河中心的距离和到盘中平面的距离的函数，然后将这些量的变化率与动力学模型进行比较，以限制盘和暗晕中的引力质量分布;（3）重新检查质量巡天数据，以确定早期在一个星系中提出的恒星运动随人口年龄的系统变化是否在整个样本中得到证实。该项目的更广泛的影响包括启动科学计划NSF支持的仪器，研究生培训和指导，并在本科课程的发展，并公开演示，传播结果给广大观众的研究成果。

This project comprises an observational campaign to determine the mass distributions in the disks of large spiral galaxies, and thereby to constrain the importance of dark matter in the inner regions of these systems. The Principal Investigator has, with previous NSF support, led the development of special-purpose integral-field spectrographs (or integral-field units, IFUs) for mapping the motions of stars and gas in galaxies. With this instrumentation, he has recently completed the Diskmass Survey, acquiring multi-color broad-band imaging and integral-field rotation and velocity dispersion maps of galaxy disks oriented face-on to the line of sight. These data suggest that galaxy disks have lower mass-to-light ratios than expected, which implies that there is no large population of faint, very low-mass stars, and that dark-matter halos are dynamically important even in the galaxies' inner regions. However, the conclusions are weakened by uncertainties in the actual thicknesses of the disks along the line of sight. To remedy the situation, the Principal Investigator, his collaborators, and graduate students will conduct further observations, focusing on similar galaxies that are oriented edge-on to the line of sight. Specifically, they will (1) make photometric measurements of 20 galaxies, in strategically chosen wide and narrow infrared spectral bands that will permit the separation of stellar populations of different age; (2) make IFU measurements of the rotation speed and velocity dispersions in edge on disks, as functions of both distance from the galactic center and distance from the disk midplane, and then compare the rates of change of these quantities against dynamical models to constrain the gravitating mass distributions in the disk and the dark halo; and (3) re-examine the Diskmass Survey data to determine if earlier suggestions in one galaxy for systematic variation in stellar motions with age of the population are borne out in the entire sample. The broader impact of this project includes the launching of science programs on NSF-supported instrumentation, graduate student training and mentoring and inclusion of research results in undergraduate course development, and public presentations that disseminate results to a wide audience.